Rotary lawn mowers are by far the most common type of mower used by homeowners. In addition, both single and gangs of rotary mowers are used in large scale commercial operations. The blades in these mowers are in almost all cases a flat, rectangular steel blade sharpened on the leading edge at each end of the blade to form a cutting edge. Depending upon how careful the user is and the amount of use of the mower, the blade should be sharpened several times a year. In order to properly sharpen the blade, the blade should be removed from the mower. This requires a considerable amount of time and the proper tools, and is not a task that the homeowner can easily perform himself. Most commonly, the user must transport the mower to a professional repair shop where the blade can be properly and professionally balanced and sharpened. This of course is costly, and after repeated sharpening, the blade must be replaced.
The prior art discloses various ways of solving the blade sharpening problem, including the use of removable cutters which can be sharpened and replaced, reversible cutters and disposable cutters. One design of replaceable cutters is shown in my U.S. Pat. No. 4,651,510, issued Mar. 24, 1987 for a "Blade for Rotary Mover". However, none of the prior art designs have achieved commercial success. The lack of commercial success is attributable to a variety of reasons, including the relative high cost of the cutters, and the difficulty of removing and installing them. Also, the lack of safety considerations has prevented some prior art designs from being commercially successful. There is therefore a need for improvements in the design of blades for rotary mowers that will resolve the problem of dull cutting edges that need to be frequently sharpened. There is especially a need for a rotary mower blade design that will allow the ordinary homeowner to keep a sharp blade on his or her rotary mower. Any such improvement which will facilitate having a sharp cutting blade must be completely safe and available at a cost that will offer the user a practical alternative to professional sharpening.
In addition to the problem of maintaining a sharp cutting edge on the blade for a rotary mower, there is a further need for blade designs that will more effectively pick up grass clippings and efficiently discharge them from the mower. Although my prior U.S. Pat. No. 4,651,510 also discloses improvements along this line, the air vanes also wear and need to be replaced, and there is a need for facilitating the replacement of these air vanes.